1. Field Of The Invention
The present invention pertains to the field of separating particulate solids from gaseous streams in which the solids are entrained, as is routinely encountered in processing operations such as fluidized bed catalytic treatment of hydrocarbon feedstocks. More specifically, the present invention pertains to a method and apparatus for separating particulate solids, such as fluidized bed catalyst particles, from gaseous process streams such as streams of hydrocarbon vapors, steam and air.
2. Related Art
Numerous methods and apparatus for separating particulate solids from gaseous streams are well known. For example, the art has devoted much time and effort to the development of separators for use in in fluidized bed catalytic cracking of hydrocarbons to separate from the process streams the fine particles comprising the catalyst. Generally, the separation of particulate solids from the gaseous streams in which they are borne is accomplished by rapidly changing the direction of the solids-laden gaseous stream, often by imposing a 180.degree. change of direction upon it, so that the inertia of the particles separates them from the flowing gaseous stream. This radical change of direction of the solids-laden gaseous stream is accomplished by impinging the stream against a wall, baffle means or other structure which, as a consequence, tends to suffer abrasion and wears at a rapid rate.
U.S. Pat. No. 4,397,738 issued Aug. 9, 1983 to Thomas L. Kemp, is illustrative of a large body of art in the field. The Kemp patent discloses a process and apparatus for separating particulate solids from a solids-laden gaseous stream by directing the stream through a central, vertically positioned standpipe which is enclosed by a containment vessel and has a plurality of discharge arms disposed about the periphery of the standpipe and angled downwardly and outwardly to direct the solids-laden gaseous stream against the walls of the containment vessel. The solids drop to the bottom of the containent vessel and the gases rise to the top of the vessel and are passed through a second stage of separation in a cyclone separator also contained within the vessel.
The art provides numerous other structures for effectuating such gaseous-solids separation, including those in which a second stage of separation is conducted in cyclones which are external to the containment vessel. Some of the difficulties encountered in effectuating solids/gas separations of this type are the high temperatures often encountered and the highly abrasive, sand blasting-like action of the solids laden gaseous stream as it passes through the equipment. The direct impingement of the solids in the high temperature gaseous stream tends to rapidly erode the equipment, particularly refractory linings usually provided on the containment vessel, and bends or elbows in conduit piping, thereby requiring frequent replacement with concomitant down time and expense. Further, mechanical structures emplaced within the containment vessel to effectuate separation are subject to high temperatures and thermal expansion and contraction, which tends to shorten their useful life.
The present invention provides a method and apparatus for effectuating separation of particulate solids from gaseous streams, including gaseous streams at elevated temperatures containing a high loading of extremely fine, abrasive particles, such as encountered in fluid catalytic cracking of hydrocarbon process streams. The present invention alleviates wear problems engendered by the "sand-blasting" action of the solids-laden gaseous stream and provides a highly efficient separation.